1. Field of the Invention
This invention relates generally to the deployment of bands of substantially cylindrical shrinkable polymer material as clamps, for example for elastomeric hose and tubing connections and, more particularly, to a mechanism which assists in the proper deployment, positioning and installation of such a substantially cylindrical shrinkable clamp. More specifically, the present invention relates to a device for mounting and deploying a substantially cylindrical shrinkable clamps without significantly effecting the constrictive force of such a clamp against a joint.
2. Description of the Prior Art
Conduits in the form of reinforced elastomeric hose and tubing are commonly used to convey various fluids which may be under a variety of pressures and temperatures. Junctions between hoses or between hoses and the items with which they communicate must be fluid tight at all temperatures and be able to resist separation that would otherwise occur because of the influence from fluid pressure, i.e. blow-off, as well as the surrounding environment, such as pull-off. Commonly, these connections are made by placing the open end of a hose over a mounting stem or the open end of two hoses over a coupling insert. The hose and associated insert are typically sized and shaped to allow the open end of the hose to slip over the stem or insert and to seat with a snug fit. In many instances, a hose clamp is then installed proximate the open end of the hose to constrict the hose tightly on the stem or insert to assist in resisting leakage, blow-off and pull-off.
Hose clamps are available in a wide variety of styles, shapes and constructions. A common type of hose clamp is in the form of an adjustable mechanical clamp wherein a metal band forms a loop that encircles the tubing joint, and this loop is then reduced in diameter by any number of known mechanical means, such as a threaded screw mechanism, a racheting mechanism and the like. Typical examples of these types of mechanical clamp devices are disclosed in U.S. Pat. Nos. 2,795,835; 2,825,114; 2,864,149; 2,865,077; 2,934,805; 3,808,643; 4,308,648; 4,402,113; 4,480,359; 4,572,552; 4,574,434; 4,843,686; 5,115,541; 5,157,815; 5,188,400; 5,329,673; 5,548,876; 5,560,087; 5,607,190; 5,642,891 and 5,647,614.
This mechanical style of hose clamp is generally simple in construction and can produce relatively substantial dynamic and static hoop stresses. Dynamic hoop stress is a constrictive force the clamp exerts upon the clamped object as a result of the inner diameter of the clamp being actively reduced. The static hoop stress is the constrictive force the clamp exerts upon the clamped object when encountering an expansion force being exerted upon the clamp by an active expansive attempt by the clamped object, such as fluid expansion within an elastomeric hose due to an increase in fluid temperature. Depending upon the hose clamp construction, these two stresses can be the same or different. Mechanical clamps typically exert a high hoop stress which results in a clamping connection with a high resistance to both blow-off and pull-off. However, mechanical clamps typically suffer from a number of disadvantages. Since such clamps are generally constructed from a strap, they have two relatively sharp edges that ring the connection end of the hose which provides an opportunity for hose damage and failure. Depending upon the metal from which the mechanical clamp is formed, it can also be susceptible to corrosion. The screw housing mechanism can also protrude from the strap thereby taking up sometimes valuable space and providing a place for objects of the environment to become entangled. Moreover, the nature of the closure mechanism generally requires a tool for operation, and sometimes valuable free space within which to operate the tool.
However, the most significant disadvantage of a mechanical clamp, at least in current automotive system applications, is its inability to resist cold fluid leaks over time. A cold leak occurs when the current system is cold and is the most prevalent and persistent type of leakage problem in modern automotive coolant systems. A common source for cold leaks is where a combination of elasticity and coefficient of thermal expansion of the clamping material is inadequate to follow the contraction of the stem or coupling insert material as both cool. After only a few heating cycles of the cooling system, the thermal expansion activity of the stem or insert and the clamp causes some of the material of the hose to flow from between the stem or insert and the clamp. This leads to an effective loosening of the clamp. Then, as the systems cools, the stem or insert shrinks away from the inner surface of the hose and the seal is broken, thereby providing a source of cold leaks.
Cold leaks are also prevalent when the hose clamp deployed exerts a non-uniform constrictive force about the circumference of the connection under the hose. Such non-uniformity also leads to leaks at times other than when the system is cold. In either event, non-uniformity can allow a separation between the stem and the hose thereby braking the seal and allowing a leak. Therefore, mechanical hose clamps also suffer from applying a non-uniform constrictive force, particularly where the housing joins the strap and at the point where the ends of the strap overlap due to both the geometry of the clamp and the relative rigidity of the material of the clamp.
In attempts to obviate the above enumerated problems associated with mechanical hose clamps, a number of polymer clamping mechanisms have been developed. In such systems, a ring of polymer material encircles a conduit or tubing joint. In some examples, this polymer material is then cross-linked to the tubing joint itself. In other instances, the polymer material is shrunk, generally by utilizing heat, to constrict it to the tubing joint. Examples of such polymer clamps are illustrated in U.S. Pat. Nos. 4,070,044; 4,366,011; 4,780,158; 4,931,116; 4,952,437; 5,071,170; 5,137,591; 5,169,176; 5,175,032; 5,228,387; 5,306,368 and U.K. Patent 2,031,106; U.K. Patent 2,1082,110; Japanese Patent 56-51324; Japanese Patent 56-75825 and Japanese Patent 58-62012.
U.S. Pat. Nos. 5,340,167; 5,531,483 and 5,566,988 are all directed toward a heat shrinkable polymer hose and tubing clamp that is designed to tightly shrink about a tubing joint when a specific diameter reducing release temperature is reached, thereby causing the clamp to immediately and tightly shrink about the tubing joint. This particular type of shrinkable polymer hose and tubing clamp is especially useful since it is self-adjusting so as to accommodate the effects of temperature and age upon hoses or tubing and stem or inserts and thus is very effective against cold leaks. This particular shrinkable polymer hose and tubing clamp is relatively flexible which allows it to both exert a uniform constrictive force and to conform to irregularities in the shape of either the hose or the stem or insert. It also provides adequate hoop stresses to prevent blow-off and pull-off of hoses associated with automotive coolant systems, is resistant to corrosion, is lightweight and is devoid of projections that waist space and can be a source for collection or debris.
While the shrinkable polymer clamps appear to obviate all of the problems previously associated with mechanical hose and tubing clamps, their installation capability has been less than satisfactory. A significant problem experienced with shrinkable polymer hose and tubing clamps is that they tend to shrink quickly, and sometimes prematurely, thereby making their installation both difficult and chancy. While the theoretical diameter reducing release temperature for heat sensitive shrinkable clamps is such that it would allow installation of the clamp about the joint prior to exposing the clamp to its diameter reducing temperature, the reality of the situation is that the diameter reducing release temperature at which heat shrinkable clamps constrict is too low for normal factory installation and operation. This situation causes premature constriction of such clamps thereby making factory installation difficult at best and eliminating any possibility of after market use for such clamps. Thus, there is a significant need for a device or system that will assist in maintaining a shrinkable hose clamp in its enlarged, pre-constriction condition and diameter so that the clamp may be mounted into its appropriate and desired position prior to its being released to constrict against the hose or tubing joint. Moreover, such a device or system cannot interfere with the ability of the shrinkable polymer clamp to tightly constrict about the hose and tubing joint while providing sufficient dynamic and static hoop stresses to resist blow-off and pull-off.